(a) Field of the Invention
The present invention relates to an adaptive receiving system and method for a MIMO (multi-input multi-output). More specifically, the present invention relates to a system and method for detecting transmit signals when channels are time-varying in wireless communication systems which use multiple transmit and receive antennas for high-speed data transmission.
(b) Description of the Related Art
As industries and personal lives using communication technologies have become activated, the importance of image and data transmission has grown while needs of high-speed data transmission have also increased. Therefore, techniques which increase data rates per bandwidth are required since the bandwidth for high-speed data transmission is insufficient.
MIMO systems for using multiple transmit and receive antennas and transmitting data in parallel have been aggressively studied so as to raise the data rates, and the V-BLAST (Vertical Bell Labs Layered Space Time) scheme has been developed as effective receivers for the MIMO systems.
The V-BLAST scheme increases bandwidth efficiency in proportion to the number of antennas when the number of antennas at a receiver is more than the number of antennas at a transmitter, and a channel is not varied for one packet duration.
However, the actual wireless mobile communication channels are varying, and computational complexity is abruptly increased when the V-BLAST scheme is applied to the channel-varying environment. That is, it is needed to estimate a MIMO channel and calculate a nulling vector corresponding to the MIMO channel in order to perform V-BLAST detection. Calculation of the nulling vector is performed once for each frame when the channel is not varying within the frame, and it is needed to calculate the nulling vector for each symbol when the channel is varying.
Methods for approximately updating the nulling vector and tracking the channel when using a V-BLAST receiver in the time-varying channel have been proposed so as to reduce the computational complexity.
A single frame is divided into several small blocks, the channel tracking is applied to each block, and the nulling vector is updated in the approximation method for updating the nulling vector and tracking the channels.
Since the above-noted method has a tradeoff between complexity and detection performance according to sizes of the blocks divided from the single frame, the detection performance is steeply worsened when the channels are varied quickly.